Benefit Plans and Other Postretirement Benefits, Pension Plan Benefit Obligations, Cash Flows and Benefit Costs (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Jan. 31, 2019		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Change in Fair Value of Plan Assets [Roll Forward]
Defined Benefit Plan, Plan Assets, Payment for Settlement			$ 198		$ 174
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Settlement Charge Recognized in Operating and Maintenance Expenses			2,352		2,270		$ 2,300
Significant Assumptions Used to Measure Costs [Abstract]
Liability, Defined Benefit Plan, Noncurrent			994		1,042
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation at Dec. 31			3,275		3,612
Change in Projected Benefit Obligation [Roll Forward]
Obligation at Jan. 1	$ 3,477		3,828		3,682
Service cost			94		94		92
Interest cost			133		147		160
Plan amendments			0		(13)
Actuarial loss			(224)		259
Defined Benefit Plan, Benefit Obligation, Contributions by Plan Participant			0		0
Defined Benefit Plan, Benefit Obligation, Prescription Drug Subsidy Receipt			0		0
Benefit payments			(354)		(341)
Obligation at Dec. 31			3,477		3,828		3,682
Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at Jan. 1	2,742	[1]	3,088	[1]	2,856
Actual return (loss) on plan assets			(142)		411
Employer contributions			150		162
Benefit payments			(354)		(341)
Fair value of plan assets at Dec. 31			2,742	[1]	3,088	[1]	2,856
Funded Status of Plans at Dec. 31 [Abstract]
Funded status			(735)		(740)
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost [Abstract]
Net loss			1,633		1,709
Prior service (credit) cost			(20)		(25)
Total			1,613		1,684
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates [Abstract]
Current regulatory assets			94		100
Noncurrent regulatory assets			1,446		1,511
Deferred income taxes			19		19
Net-of-tax accumulated other comprehensive income			54		54
Total			$ 1,613		$ 1,684
Significant Assumptions Used to Measure Benefit Obligations [Abstract]
Discount rate for year-end valuation (as a percent)			4.31%		3.63%
Expected average long-term increase in compensation level (as a percent)			3.75%		3.75%
Mortality table			RP-2014		RP-2014
Cash Flows [Abstract]
Total contributions to Xcel Energy's pension plans during the period			$ 150		$ 162		125
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			94		94		92
Interest cost			133		147		160
Expected return on plan assets			(209)		(209)		(210)
Amortization of prior service cost (credit)			(5)		(2)		(2)
Amortization of net loss			111		107		97
Settlement charge			91		81		0
Net periodic benefit cost			215		218		137
Costs not recognized due to regulation			(75)		(79)		(15)
Net benefit cost recognized for financial reporting			140		139		$ 122
Settlement Charge Recognized in Operating and Maintenance Expenses			$ 11		$ 8
Significant Assumptions Used to Measure Costs [Abstract]
Discount rate (as a percent)			3.63%		4.13%		4.66%
Expected average long-term increase in compensation level (as a percent)			3.75%		3.75%		4.00%
Expected average long-term rate of return on assets (as a percent)			6.87%		6.87%		6.87%
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant			$ 0		$ 0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Current Regulatory Liabilities			0		0
Amounts Not Yet Recognized As Components Of Net Periodic Benefit Cost Recorded As Noncurrent Regulatory Liabilities			0		0
Liability, Defined Benefit Plan, Current			0		0
Liability, Defined Benefit Plan, Noncurrent			735		740
Defined Benefit Plan, Amounts for Asset (Liability) Recognized in Statement of Financial Position			$ (735)		$ (740)
Subsequent Event | Pension Plan [Member]
Cash Flows [Abstract]
Total contributions to Xcel Energy's pension plans during the period	$ 150

[1] (a) See Note 10 for further information regarding fair value measurement inputs and methods.